For years, as a conservative radio talk show host, I played a role in that conditioning by hammering the mainstream media for its bias and double standards. But the price turned out to be far higher than I imagined. The cumulative effect of the attacks was to delegitimize those outlets and essentially destroy much of the right’s immunity to false information. We thought we were creating a savvier, more skeptical audience. Instead, we opened the door for President Trump, who found an audience that could be easily misled.